Equation of state modeling with pseudoatom molecular dynamics

Area of Science:

• Materials Science
• Computational Physics
• Geophysics

Background:

• Accurate equations of state are crucial for understanding material behavior under extreme conditions.
• Silicon dioxide (SiO2) is a geophysically significant material found abundantly in the Earth's mantle.
• Previous models often struggle to accurately capture the complex thermodynamic properties of SiO2.

Purpose of the Study:

• To develop a robust equation of state for silicon dioxide.
• To validate the modified pseudoatom molecular-dynamics (PAMD) approach for complex materials.
• To compare ion thermal contributions with existing theoretical models.

Main Methods:

• Utilized a modified pseudoatom molecular-dynamics (PAMD) approach.
• Generated equations of state for silicon (Si) and oxygen (O) individually.
• Constructed the equation of state for silicon dioxide (SiO2) from component data.
• Performed ab initio simulations for silicon pressure validation.
• Compared PAMD-derived thermodynamic functions with one-component plasma and charged-hard-sphere models.

Main Results:

• Successfully generated the equation of state for silicon dioxide.
• Demonstrated close agreement between PAMD results and ab initio simulations of silicon pressure.
• Showed excellent correlation with experimental shock Hugoniot data for silicon dioxide.
• Provided insights into ion thermal contributions to thermodynamic functions.

Conclusions:

• The modified PAMD approach is a reliable method for determining the equation of state for complex materials like SiO2.
• The generated equation of state for SiO2 is validated by both theoretical simulations and experimental data.
• This work advances the understanding of SiO2 thermodynamics under high-pressure conditions relevant to geophysics.